\documentclass[]{article}
\setlength{\pdfpagewidth}{8.5in} \setlength{\pdfpageheight}{11in}
\begin{document}
\begin{tabular}{lcccccc} \hline
 & (1) & (2) & (3) & (4) & (5) & (6) \\
 & Instrument excl. neighbors & Instrument excl. countries within 500km & Instrument excl. countries within 750km & Instrument excl. countries within 1000km & Instrument includes neighbors & Instrument includes pop. weights \\
VARIABLES & Electoral democracy index & Electoral democracy index & Electoral democracy index & Electoral democracy index & Electoral democracy index & Electoral democracy index \\ \hline
 &  &  &  &  &  &  \\
Arms technology lag = L, & 0.55*** & 0.54*** & 0.71*** & 0.86*** & 0.52*** & 0.53*** \\
 & (0.18) & (0.18) & (0.23) & (0.28) & (0.16) & (0.17) \\
Lag GDP per capita (log) = L, & -0.20*** & -0.20*** & -0.21*** & -0.23*** & -0.20*** & -0.20*** \\
 & (0.05) & (0.05) & (0.06) & (0.06) & (0.05) & (0.05) \\
 &  &  &  &  &  &  \\
Observations & 1,882 & 1,882 & 1,882 & 1,882 & 1,882 & 1,882 \\
Sample & Excl. WEU & Excl. WEU & Excl. WEU & Excl. WEU & Excl. WEU & Excl. WEU \\
Kleibergen-Paap F-statistic & 39.85 & 43.23 & 17.17 & 13.49 & 56.74 & 44.34 \\
 Countries & 127 & 127 & 127 & 127 & 127 & 127 \\ \hline
\multicolumn{7}{c}{ Robust standard errors in parentheses} \\
\multicolumn{7}{c}{ *** p$<$0.01, ** p$<$0.05, * p$<$0.1} \\
\end{tabular}
\end{document}
